The present invention relates to the field of archery and in particular to broadhead arrowheads often referred to simply as broadheads.
Broadheads having blades that are held in a retracted configuration during flight that are moved to a deployed, expanded position when the arrow strikes the target are well known in the art. These mechanical broadheads overcome the wind drag and stability problems associated with fixed-blade broadheads. Mechanical broadheads can be classified generally into two categories. Broadheads in which the movable blades are pivoted rearward of the center of the blade so that the blades are swept forward during flight are often referred to as “forward-deployed” mechanical broadheads. U.S. Pat. No. 6,217,467 to Maleski and U.S. Pat. No. 6,595,881 to Grace, Jr. et al. are examples of forward-deployed mechanical broadheads. In each case, because the blades are pivoted behind the center of the blade, as the blade strikes the target, a torque couple is generated about the pivot access which causes the blades to pivot outwards and backwards approximately 120 degrees to form the broadhead arrow tip. Forward-deployed mechanical broadheads have an advantage in that the deployment mechanism is simple and straightforward, however, they suffer from the disadvantage that since the blades must move through such a large angle, the reaction forces exert significant stress on the blades and hinge, and substantial impact energy is consumed by the deployment process. Prior art forward-deployed mechanical broadheads also suffer from the fact that in the deployed configuration, the blades are typically locked to the ferrule. Accordingly, if one blade strikes an obstruction, such as a heavy bone, the impact may deflect the arrow's trajectory, significantly reduce the depth of penetration into the target, and/or damage the blade.
Mechanical broadheads in which the blades are pivoted forward of the center of the blade so that the blades are swept backwards during flight are often referred to as “rearward-deployed” mechanical broadheads. U.S. Pat. No. 6,270,435 to Sodaro discloses a rearward-deployed mechanical broadhead in which the blades are spring loaded toward the deployed configuration. The blades are retained for flight by a retaining ring that is dislodged during impact to allow the blades to move to their deployed configuration. U.S. Pat. No. 7,717,814 to Sanford discloses a rearward-deployed mechanical broadhead in which the blades are spring loaded toward the deployed configuration. The blades are held in the retracted configuration for flight by means of a catch that is released when a plunger element strikes the target. As can be determined from the foregoing, although rearward-deployed mechanical broadheads have the advantage of using less impact energy for deployment, they suffer from a high degree of mechanical complexity and cost. Prior art rearward-deployed broadheads also suffer from the fact that the blades in the deployed configuration are effectively locked to the ferrule by the deployment springs, and therefore, if a blade strikes an obstruction, the arrow is likely to be deflected, penetration significantly reduced, and/or the blade damaged.
U.S. Pat. No. 6,910,979 to Barrie et al. discloses a rearward-deployed mechanical broadhead in which the blades translate rearward by the interaction with the target. As the blades translate rearward, they are cammed outward along a track that causes the blades to extend outward to a locked, deployed configuration. The mechanical broadhead of Barrie et al. is considerably less complex then the spring-loaded rearward-deployed mechanical broadheads of Sodaro and Sanford, however, because the blades of Barrie et al. in the deployed configuration are still locked to the ferrule, the Barrie broadhead suffers from the same vulnerability if a blade strikes an obstruction.